1. Field of the Invention
The invention relates to geometrical instruments, particularly of the straight edge type with a levelling feature of the square type. Specifically, the invention relates to a tool for conduit bending and metal bending, that is also a pocket level and small increment measuring tool.
2. Description of the Prior Art
Tools for leveling and squaring are known in a variety of configurations particularly in the carpentry trades. U.S. Pat. No. 613,946 to Starrett discloses a three way level and square that is adaptable to forming plumb right angles by means of two perpendicular arms, each having a level on one mutually coplanar face and one of the arms having a level on a second face on the surface opposite from the right angle. Variations and improvements on the above device are reflected in U.S. Pat. No. 1,963,805 to Radke and U.S. Pat. No. 3,524,259 to Handley, both of which relate to level devices applied to squares. The Radke device consists of a square with mutually facing levels on the two arms thereof and a fastening slot in one of the arms on the surface opposite from the level vial. This device is clamped over one leg of a larger square and is provided with means for angularly altering the relationship between the two squares. The Handley device provides three coplanar level vials, one aligned with each leg of a square and one at 45 degrees to each leg, located at their intersection.
Special squares and levels for plumbers and pipe fitters have taken into account the need to fit the square against round pipes, as shown in U.S. Pat. No. 3,826,013 to Baher, while other devices have combined squaring and measuring functions, as reflected in U.S. Pat. No. 2,816,269 to Becker and U.S. Pat. No. 1,400,626 to Rodriguez. The latter two devices provide means for linear measurement as well and angular measurement to aid in properly aligning pipes. While most levels provide an indication of only certain preselected angles, it is also known to provide measurement of a range of angles and to attach the level to a workpiece by a clamp, as taught in U.S. Pat. No. 3,071,863 to MacMillan for a wheel alignment gage.
While each of the known levels and squares is adapted to a specific job, none has proven satisfactory for use in determining the accuracy of pipe and conduit bends on the many types of pipe benders in common use, especially at work sites. Such benders may be electrical or manual, and often have tight working clearances between the pipe and portions of the bender, such as the bending shoes. Because many types of benders may be encountered, including the "hickey" benders operated by either hand or foot, pipe benders have become self-reliant to judge the accuracy of bends, but in those pipes having more than a single bend it is very difficult for the eye to accurately align the pipe for the second bend, which must be properly aligned with the first so that the pipe will continue to lie in a single plane. It is therefore desirable that a single, portable, widely applicable tool be created that can be accurately and easily applied to aid in bending pipe by any of the known apparatus employed for that purpose.